Liquid Natural Gas Carrier Research Articles

Dynamic roll instability of liquid natural gas carrier during offloading operations and prediction of downtime cost in Malaysian waters

The loss of revenue or global loss in term of cost due to downtime conditions is always a concern for field operators. Prevailing wave conditions may suddenly appear during offloading operations, which will influence the overall process and may lead to downtime of operations. Severe weather can significantly impact downtime costs of offloading operations and cause a huge loss of revenue. This research work integrates the dynamic stability with downtime cost for LNG carrier in different location of Malaysian waters using real time metocean data. This study on downtime cost utilizes the real time and location-specific wave scatters, as well as limiting criteria of offloading in Malaysian waters. The dynamic roll stability of LNG carrier was investigated for ABS criteria in two depths of water at three real-time locations. Susceptible wave conditions had been identified along with downtime cost analysis. This domain of downtime cost study was further rendered into mathematical package in the form of graphical interfaces for field operators. This mathematical based graphical interface facilitates in predicting location-specific downtime cost charts and allows operator companies to determine the fiscal losses for different range of downtime days and various capacities of LNG carrier. Overall, this research contributes by linking dynamic stability with operating costs through real time metocean data in Malaysian waters.

ANALYSIS OF THE MAIN GENERATOR DUAL FUEL DIESEL ELECTRIC (DFDE) 12V50DF SUDDEN TRIP

In the 20th century, the growth of marine transportation has grown rapidly in line with technological advances. Given that the marine transportation sector is one of the pollutants that exist today, the use of energy sources with better thermal efficiency and combustion that does not have a negative impact on the environment is needed in the modern era. In accordance with the regulations stipulated by IMO in the Marine Polution (Marpol) Annex VI Regulation 14 which regulates the prohibition of ships from using fuels with sulfur content higher than 0.5%. The need for alternative fuels in the shipping industry is an important thought to support the efficiency of the shipping industry. Liquid Natural Gas (LNG) is currently being developed by the government as a fuel for vehicles and environmentally friendly industries. In addition to its availability, natural gas is also considered effective for combustion. Methane / LNG gas is one of the most dominant alternative fuels at this time. This fuel can also save company expenses, namely reducing the cost of providing fuel for energy needs as a source of propulsion on board the ship. For the above, ships, especially LNG carriers, have used a lot of diesel engines to propel their ships using LNG fuel with the concept of the engine being Two Fuel Diesel Electric (DFDE) where the engine can use Marine Diesel Oil (MDO) and LNG. The DFDE engine drives the Generator and the Generator generates electricity to drive the Electric Motor and the Electric motor moves the propeller shaft, this DFDE engine in the future will replace conventional diesel engines because it is more cost efficient, but requires Engineers who understand DFDE engine technology.

A New Consideration About Floating Storage and Regasification Unit for Liquid Natural Gas

In this paper we want to present the details of new project about floating liquid natural gas (LNG) regasification terminal based on conversion of an existing LNG carrier . LNG is sent from the tanks to the regasification skid fwd. The regasification skid essentially comprises booster pumps and vaporizers This project can boost both transport and economy sector of Central European countries by introducing a less expensive fuel, more environmental friendly and with a good perspective in the future. The project consists in building a LNG import terminal in Constanta, harbor from where the merchandise (LNG in this situation) can easily be delivered on Danube’s basin and reach central European countries.

Numerical Study of 3-D Liquid Sloshing in an Elastic Tank by MPS-FEM Coupled Method

The sloshing phenomenon in a partially loaded oil tanker or liquid natural gas ship is a typical fluid-structure interaction problem involving multi-physics, violent free-surface flow, and nonlinear structural response. In the past decades, the complex phenomenon has been commonly investigated without consideration of the hydro-elastic behaviors of the bulkheads. In our previous work, the liquid sloshing phenomenon in a two-dimensional (2-D) elastic tank was numerically studied. However, the bulkheads of the tank will deform within the three-dimensional (3-D) space in reality. So, it is necessary to study the 3-D sloshing problem in an elastic tank. In this article, a hybrid approach is developed within the Lagrangian system. The moving particle semiimplicit (MPS) method is used to simulate the evolution of 3-D flow with a violent free surface, and the finite element method (FEM) is used for the numerical analysis of structural response due to the impact loads of the sloshing flow. To couple the MPS method and the FEM method, an interpolation scheme based on the kernel function of the particle method is proposed for the communication on the isomerous interface between the fluid and structure domains. The reliability of force and deformation interpolation modules is validated by two tests. Then, the sloshing phenomenon in a 3-D elastic tank is numerically investigated and compared against the previous published 2-D results. By varying the Young's modulus of the tank walls, characteristics regarding the evolutions of free surface, variation of impact pressures, and dynamic responses of the structures are presented. 1. Introduction To support the transportation demands of natural resources, more and more vessels, such as the very large crude carriers and the liquid natural gas carriers, are manufactured. For these huge structures, risks such as local deformation or even damage of cargo-containment systems resulting from sloshing phenomena subsequently increase. Therefore, it is necessary to take the elasticity of the tank walls into account in the research of sloshing phenomena (Dias & Ghidaglia 2018). However, the phenomena involving the vibrations of the tank walls are complex. In the process of sloshing wave interacting with elastic bulkheads, the fragmentation, splash, and fusion of water are observed. Meanwhile, the structures vibrate nonlinearly under the impact loads resulting from the sloshing wave. These phenomena are hard to simulate realistically by the traditional mesh-based methods.

Pressure Control of Insulation Space for Liquefied Natural Gas Carrier with Nonlinear Feedback Technique

This paper introduces a novel control strategy into the insulation space for liquid natural gas carriers. The control strategy proposed can improve the effects of control for differential pressure and reduce the energy consumption of nitrogen. The method combines a nonlinear feedback technique with a closed-loop gain shaping algorithm (CGSA). It is designed for the pressure control system which is vital for liquid natural gas carriers (LNGCs) in marine transportation. The control error is modulated using nonlinear function. The deviation signal is replaced with a nonlinear feedback signal. Comparison experiments are conducted under different conditions to prove the effectiveness of this strategy. This paper compares three control strategies: a control strategy with nonlinear feedback based on CGSA, a control strategy without nonlinear feedback based on CGSA, and a two-degree-of-freedom (DOF) control strategy. The simulation results show that this control strategy with nonlinear feedback performs better than the other two. The average reduction of control input is about 38.8%. The effect of pressure control is satisfactory.

Application of Steam Jet Injector for Latent Heat Recovery of Marine Steam Turbine Propulsion Plant

Abstract This paper presents the results of previously carried out analyses regarding efficiency and criteria evaluation of various propulsion plants of modern LNG (Liquid Natural Gas) carriers. The results of previous identification and quality assessment of waste heat energy sources of a CST (Conventional Steam Turbine) plant are presente. In this paper the possibility of use a steam jet injector in order to recover the latent heat is analysed. Calculations were carried out for an injector equipped with a de Laval nozzle, determining the thermodynamic state parameters of the mixture of drive steam and sucked in steam as well as the steam on the outlet of the injector for the various ejection ratios. On the basis of the results of the injector calculation, the heat balance of a simple regenerative Clausius – Rankine steam cycle (with one regenerative heater – deaerator) was carried out. The degree of regeneration (increase of the thermal efficiency) for cycle using the regenerative injector was determined. Based on results the further research directions for complex plants using a steam jets are indicated.

Structural safety assessment for FLNG-LNGC system during offloading operation scenario

The crashworthiness of the cargo containment systems (CCSs) of a floating liquid natural gas (FLNG) and the side structures in side-by-side offloading operations scenario are studied in this paper. An FLNG vessel is exposed to potential threats from collisions with a liquid natural gas carrier (LNGC) during the offloading operations, which has been confirmed by a model test of FLNG-LNGC side-by-side offloading operations. A nonlinear finite element code LS-DYNA is used to simulate the collision scenarios during the offloading operations. Finite element models of an FLNG vessel and an LNGC are established for the purpose of this study, including a detailed LNG cargo containment system in the FLNG side model. Based on the parameters obtained from the model test and potential dangerous accidents, typical collision scenarios are defined to conduct a comprehensive study. To evaluate the safety of the FLNG vessel, a limit state is proposed based on the structural responses of the LNG CCS. The different characteristics of the structural responses for the primary structural components, energy dissipation and collision forces are obtained for various scenarios. Deformation of the inner hull is found to have a great effect on the responses of the LNG CCS, with approximately 160 mm deformation corresponding to the limit state. Densely arranged web frames can absorb over 35% of the collision energy and be proved to greatly enhance the crashworthiness of the FLNG side structures.

Comparison of sloshing-induced pressure in different scale tanks

This paper considers scale effects on three-dimensional (3D) sloshing flows. A series of model tests were conducted for three differently scaled tanks. The model tanks considered in this study were 1:70, 1:50, and 1:30 scaled membrane type tanks based on a 138,000 m3 liquid natural gas carrier model. The tests were carried out for harmonic sway and roll motions for three different filling depths and with various excitation frequencies. The pressure measuring points in the tanks were the same, as if they were scaled up to actual size. The main parameters investigated in this study were the pressure peak and rise time of sampled sloshing pressures. These key sloshing load parameters were systematically analysed by a statistical approach, and the results from the tests at different scales were compared.

Optimization procedure for liquid natural gas carrier structural design

The purpose of this article is to present the design procedure and the main results of its validation through the liquid natural gas carrier structural optimization. The work has been carried out through the EU FP6 project IMPROVE. The objective of the developed optimization process was to distribute the material more effectively in order to reduce weight/cost and to improve the structural safety in the allocated time frame. A coarse mesh finite element method model (three holds) has been developed, using MAESTRO software. Strength calculation has been carried out according to the Bureau Veritas Rules for direct calculation. Sensitivity analysis has been performed to investigate the influence of web frame spacing, longitudinal stiffener spacing and material type on the specified design objectives. Design procedure applied for the structural optimization of the liquid natural gas structure (one cargo hold) resulted in mass decrease of about 424 t (after standardization of scantlings), or 10.8%; the cost of the structure was reduced by about 5%; structural safety was increased and vertical center of gravity was slightly reduced by about 20 cm compared to the prototype structure.

B. Vessel Source Pollution

The new Chapter 4 of MARPOL Annex VI entered into force on 1 January, which includes requirements mandating the Energy Efficiency Design Index (EEDI) for new ships and the Ship Energy Efficiency Management Plan for all ships (see last year’s report). The Marine Environment Protection Committee (MEPC) held its sixty-fifth session (MEPC-65) on 13–17 May. MEPC-65 approved amendments to MARPOL Annex VI with a view to adoption next year, to extend the application of EEDI to (roll on / roll off (ro-ro)) cargo ships (vehicle carrier), liquid natural gas carriers, cruise passenger ships having non-conventional propulsion, ro-ro cargo ships and ro-ro passenger ships; and to exempt ships not propelled by mechanical means, and platforms including FPSOs and FSUs and drilling rigs, regardless of their propulsion; as well as cargo ships having ice-breaking capability.

Experimental Investigation of Invar Edge Effect in Membrane LNG Tanks

Sloshing, a violent fluid motion in tanks is of current interest for many branches of the industry, among them gas shipping. Although different methods are commonly combined for analyzing sloshing in liquid natural gas (LNG) carriers, time histories of the pressure in the tanks are most reliably obtained by experiments. Very localized pressures may be important for the structural response of the tank containment system. Moreover, the typical pressure time history duration is similar to the structural natural frequency. Therefore, pressure measurements need to be performed with due account for temporal and spatial distribution. This requires a high sampling resolution both in time and space. Fine spatial resolution becomes especially important when local pressure effects are of interest, such as pressure profile passing a membrane corrugation of Mark III containment or Invar edge of No. 96 containment. In this paper experimental approach applied by MARINTEK for analyzing sloshing phenomenon is presented. The focus is put on investigating effects of Invar edges. A transverse 2D model of a typical LNG carrier is used. Local pressure effects are investigated based on low filling level tests with different wall surfaces: smooth and with horizontal protrusions representing the surface similar to the No. 96 containment system.

Development of Ultra-Steam Turbine (UST) in High-pressure/High-temperature Reheat Steam Turbine Plant for LNG Carriers

Since the steam turbine plant have flexibility of fuel selection (oil only, gas only and dual), most propulsion plants for Liquid Natural Gas Carriers (LNGC) have been the steam turbine plant. However, the rising prices of fuel and shortage of the crew for the steam turbine plant, the movement to investigate higher efficiency propulsion plant has gotten active. Actually, a lot of LNGCs for European owners have adopted dual fuel diesel engine (DFE) with electric propulsion motor, and many large size LNGCs (200, 000 m3) built in Korean shipyard have adopted diesel engine with re-liquefaction plant (DRL) recently. Under such a situation, we propose new high efficiency plant; UST (Ultra Steam Turbine Plant) that has advantages of conventional steam turbines (high reliability, safety, low maintenance cost and easy operation) for the restitution of steam turbine plant, the recovery of the share and the exploitation of the new market. In this paper, we introduce the outline of the UST plant, and present the features and key technology of reheat turbine that is one of main components of UST plant.

The Lay-Up and Reactivation of LNG Tankers: Lessons Learned

The Liquid natural gas (LNG) industry went from a projected boom in the 1970's to a contracted industry in the 1980's, when many ships were either permanently or temporarily laid up. In the 1990s, many laid-up LNG carriers are being reactivated after as many as 12 years in lay-up. While the capital cost of an LNG carrier should dictate maximum preservation of the asset, the LNG industry is not immune to having to make hard economic decisions during slack times. In this paper, the authors present specific alternate lay-up procedures, together with the relative costs of these alternatives. LNG carriers are steam vessels, as are many of the vessels in the Ready Reserve Fleet (RRF). However, many of the conclusions reached can also be applied to motor vessels, and as such could be of interest to operators and shipyards in all phases of the RRF program. The subjects of dehumidification, inert gas plants, ballast tank coatings and drydocking, among others, are discussed.

LNG carrier underwater noise in Baffin Bay

Large powerful liquid natural gas carriers may soon ply Arctic waters year round. Concern has been expressed over the impact the resulting noise will have on Arctic marine life. This study includes estimates of LNG carrier-radiated noise source levels and resulting sound levels at a given distance from the ship for a number of operating conditions. Measurements of sound propagation and ambient noise conditions in Baffin Bay are used to estimate the ship noise levels in relation to the summertime noise background.